I quit using incense when I got rats, because all that emits is smoke. Esp if you are using synthetic fragrances with anything candles, air fresheners etc. Some contain phthalates which to me are not good. I do not burn candles in my home, but I make my own wickless candles, wax tarts, soap etc. I use to diffuse lemon for one of my asmatic girls I read somewhere it helped with asthma attacks it did help a bit. It depends on the essential oil too, each one may have a different warning on it. I love using essential oils in my salves though for the rats, it really helps w/healing.